A composite video signal comprises a luminance signal (Y) and a chrominance signal (C). A comb filter is commonly used to separate the luminance signal and the chrominance signal from the composite video signal. The process of separating the luminance signal and the chrominance signal is referred to as a Y/C separation.
There are three types of comb filters used to separate the composite video signal. The three types of comb filters are classified into a one-dimensional (1D) comb filter, a two-dimensional (2D) comb filter and a three-dimensional (3D) comb filter. The 1D comb filter and the 2D comb filter are referred to as a type of non-3D comb filter. In general, the non-3D comb filter is used to separate the luminance signal and the chrominance signal when an image is under a motion condition, and the 3D comb filter is used to separate the luminance signal and the chrominance signal when the image is under a static condition.
However, it is difficult to make a precise judgment between the motion condition and the static condition. When the image is under the motion condition and the 3D comb filter is wrongly used to separate the luminance signal and the chrominance signal, a mesh-like image appears due to the effect of the chrominance signal on the luminance signal. That is, the luminance signal is affected by the chrominance signal.
Therefore, there is a need for a solution to avoid the problem that the luminance signal is affected by the chrominance signal when the 3D comb filter is wrongly used under the motion condition.